Large off-highway vehicles (“OHVs”), such as mining vehicles used to haul heavy payloads excavated from open pit mines, are well known and usually employ motorized wheels for propelling or retarding the vehicle in an energy efficient manner. This efficiency is typically accomplished by employing a large horsepower diesel engine in conjunction with an alternator, a main traction inverter, and a pair of wheel drive assemblies housed within the rear tires of the vehicle. The diesel engine is directly associated with the alternator such that the diesel engine drives the alternator. The alternator powers the main traction inverter, which supplies electrical power having a controlled voltage and frequency to electric drive motors of the two wheel drive assemblies. Each wheel drive assembly houses a planetary gear transmission that converts the rotation of the associated drive motor energy into a high torque low speed rotational energy output which is supplied to the rear wheels.
Typical operating loads in an off-highway vehicle (OHV) may exceed one hundred tons, while the gross weight of vehicle and load may be several hundred tons. The weight of a single wheel drive assembly can be in excess of ten tons, and inertia of the wheel drive assembly can affect operation of the vehicle as a whole. Accordingly, it is desirable to reduce wheel drive assembly weight while maintaining strength to support and move the entire heavy vehicle.
Large components within OHV wheel drive assemblies have been fabricated as weldments, i.e., the components have been forged, bent, or pressed as separate pieces that then have been joined by welding. Such weldments can include, for example, wheel frames joining the wheel drive assemblies to the OHV frame or axle box, as well as wheel hubs to which tires are mounted. Although weldments can be made to very complex shapes at relatively low cost, and thereby have been preferred as enabling the placement of material only where needed to carry load, adequate heat treatment of very large weld joints has sometimes been challenging, and such joints have been difficult to fabricate. Accordingly, it is desirable to provide unitary wheel assembly components shaped to minimize non-load-bearing material, without being so complex as to require welded fabrication.